Pope Orders Peace Mission to Yugoslavia : Vatican: Trips to Soviet Union, Poland, Hungary are also in the works. They mark the pontiff’s growing involvement in the affairs of Eastern Europe.

Playing his strongest suit, Pope John Paul II is plunging the Vatican deeper and more directly into the maelstrom of change in Eastern Europe. The Polish pontiff Thursday ordered his foreign minister on a peace mission to Yugoslavia, where the breakaway republics of Croatia and Slovenia are heavily Catholic.

Later this month, John Paul will visit Eastern Europe for the second time this year. And, Vatican sources say, a papal visit to the Soviet Union next year, still not officially announced, is virtually certain.

Often depicted as a catalyst in the collapse of communism in the former East Bloc, John Paul has worked patiently to expand the influence of his reborn church there. By now, hierarchies have been re-established and relations resumed with the Soviet Union and all of the countries in its former bloc. John Paul has even been invited to Bulgaria, whose secret police are suspected of directing a 1981 assassination attempt against him. New ties are also envisaged soon between the Vatican and odd-man-out Albania.

Yugoslavia, where religion lies amid the roots of internal ethnic strife, has been a frequent target of papal appeals for moderation since the independence struggle began in mid-June.

The Vatican takes no position on independence, but John Paul has warned since the outset that “the rights and legitimate aspirations of peoples cannot and must not be suppressed with force.” He calls for dialogue to find “just solutions . . . and fraternal coexistence.”

The Vatican added action to rhetoric Thursday in an unusual direct move to send a high-ranking diplomat as a peace-seeker in a trouble spot while bullets are flying. Supporting European Community proposals for international peacekeeping observers in Yugoslavia, the Vatican announced that Archbishop Jean-Louis Tauran, who is effectively the Pope’s foreign minister, would go to Zagreb on Monday.

He will confer there with Yugoslav bishops who publicly support Croatia’s bid for independence.

The next day he will meet with the independence-minded Yugoslav Bishops’ Conference, which has denounced the Belgrade government’s use of force in the “new democracies” as “contrary to morality, to the respect for human rights, and to the rights of peoples to self-determination.”

Tauran’s mission is officially described in the Vatican Bulletin as “primarily ecclesiastical in character.” He is to express papal solidarity with suffering, echo the Pope’s repeated appeals for a peaceful solution and listen to the concerns of Yugoslav pastors and their flock.

The visit is likely to be more than spiritual, though. Vatican analysts said they would not be surprised if Tauran also seeks to temper the bishops’ outspoken nationalist fervor in the interests of dialogue and a peaceful settlement.

From Zagreb, Tauran goes to Belgrade on Tuesday to meet with the Orthodox Patriarch Pavle, who leads the church of the Serbian majority there, and with Yugoslav Foreign Minister Budimir Loncar.

The unspoken Vatican hope is that Tauran can tell Yugoslav officials that the Catholic leaders of Croatia and Slovenia echo their Pope’s conviction that it is wiser to talk than to fight.

John Paul returns to Eastern Europe on Aug. 13 for his fourth visit to his Polish homeland--he was last there in June--and his first to Hungary, where he will spend four days. The Polish visit is mostly for nostalgia and ceremony.

Hungary, though, will get a thorough, through-the-hustings pastoral visit of the sort John Paul has already paid to Czechoslovakia and plans eventually to extend to other reopened lands of the old Warsaw Pact.